Packages for RF power semiconductors take many forms, each having particular advantages and disadvantages. For example, packages having straight leads that extend outward beyond the sides of an insulative layer create a very long inductance path which is undesirable for RF applications. An electrically and thermally conductive metal flange which forms part of the insulative layer provides a ground connection to an RF power semiconductor die mounted to the flange. The conductive flange also dissipates heat from the RF power semiconductor die. Straight lead-type packages require manual and time consuming assembly processes for mounting the signal leads and flange onto a PCB. The PCB typically has a cavity region for receiving the flange, which is attached to a larger heat sink disposed at the backside of the PCB for greater heat dissipation capacity. A cavity may also be machined into the heat sink for receiving part of the flange. Such non-planar, non-surface-mountable packaging arrangements require manual assembly and soldering processes for manufacturing the final package-PCB structure.
Gull wing-type RF power packages have signal leads which extend outward from the top surface of an insulative substrate. While the signal leads for a gull wing package can be surface-mounted to a PCB, the leads have a very long inductive path. Long inductive paths are especially problematic for RF power applications as the frequency and power levels increase. Straight lead-type RF power packages are more common than gull wing-type packages, but are not surface-mountable due to the signal leads being offset from the base of the package as described above. Also, straight-lead power packages require specially designed PCBs and heat sinks in order to adapt to the package structure also as described above, increasing assembly time and cost.
RF power packages typically require an attachment mechanism such as a solder bond, screws, retaining spring, or a thermally conductive adhesive, for attaching the package to a PCB and larger heat sink. When an RF power package is attached to a PCB and larger heat sink by screws, one or more screw holes must be provided in both the mounting flange of the package and the larger heat sink, requiring separate assembly steps by the manufacturer of circuit boards using such RF power devices. Further, the RF power devices have input and output lead frames attached to the sides of the mounting flanges, which typically require a hand soldering step separate from the normal solder reflow process. These extra steps in the manufacturing process increase manufacturing cost and reduce yield.